This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To introduce a selectable marker such as neomycin resistance or EGFP by homologous recombination into a tissue [unreadable] specific gene.[unreadable] [unreadable] We've successfully introduced EGFP and puromycin into hSox1 located on chromosome 13q34 via homologous [unreadable] recombination. Eight clones were obtained. When these hSox1 knock in cells underwent neural differentiation, low levels [unreadable] of EGFP mRNA expression was observed via RT-PCR. The expression levels of EGFP, however, were too low for any practical [unreadable] use, indicating the low promoter activity of human Sox1 gene. This is consistent with low level expression of the [unreadable] endogenous Sox1 gene during neural differentiation of hESCs, and in contrast with the relatively high expression of Sox1 [unreadable] gene in mouse. This research uses WNPRC Stem Cell Resources, the IS Division, and federally approved human ES cell [unreadable] lines.